The long-range goal of this research is to identify a feasible means to reactivate the 3-globin gene in the adult in order to ameliorate sickle cell disease and thalassemia in the patients. The objective of this competing renewal application is to understand the mechanism which governs erythroid tissue- and stage- specific globin gene regulation (hemoglobin switching). Our central hypothesis is that the 2LCR is the organizer of a transcription factory in erythroid cells;only the gene that is looped into the factory will be transcribed;the loop-in probability is determined by the chromatin flexibility, which is modulated by epigenetic changes in chromatin, e.g., histone acetylation;the transcription potential of the globin genes is not development-specific;the developmental-specific expression of the globin genes is due to the promoter-directed developmentally specific changes in histone acetylation, and consequential alteration of the preferential interaction between the LCR and the genes. This hypothesis will be tested in three specific aims. 1) To validate the hypothesis that the ?LCR is the organizer of the transcription factory specific for the globin genes in erythroid cells. 2) To test the hypothesis that the ?-globin gene promoter regulates the developmental specificity of gene expression in two separate steps. 3) To investigate the molecular events, which lead to alterations of epigenetic modifications at the ? gene promoter and the resulting modulation of chromatin looping between the LCR and the gene. PUBLIC HEALTH RELEVANCE: The objective of this application is to understand the molecular mechanism which governs erythroid tissue- and stage-specific globin gene regulation (hemoglobin switching). To delineate this mechanism a facilitated chromatin looping hypothesis was put forward. Experiments were designed in three aims to test this model in this application.